
class Solution {
public:
    bool isPalindrome(string s) {
       int n=s.size();
       if(n==0)
       return true;
       vector<char>a;
       for(int i=0;i<n;i++){
           if(s[i]>='A'&&s[i]<='Z'){
            char t=s[i]+32;
            a.push_back(t);
           }
           else if(s[i]>='a'&&s[i]<='z')
           a.push_back(s[i]);
           else if(s[i]>='0'&&s[i]<='9')
           a.push_back(s[i]);
       }
       int m=a.size(),l=0,r=m-1;
       while(l<r){
           if(a[l]==a[r]){
               l++;
               r--;
           }
           else
        return false;
       }
 return true;
    }
};